Help identifying an ST IC.

[gkmaia]

I got a keyboard with a faulty PCB and have been trying to figure out what IC is this one. If it is a processor, gate array or what... but cannot find a datasheet anywhere.

[fzabkar]

I can't help, but here is another discussion:

http://www.dubrovenko.ru/ddssite/forum/viewtopic.php?t=232

Resources:
https://cloud.mail.ru/public/czC3/qw8fu5otT

[gkmaia]

Exactly it. From an mAudio board. Thanks for that.

The dream SAM9708 is the DSP. Feels like the ST could be processor as it has crystal beside it. Would be good to have a datasheet to test some of the pins.

There is an implementation of the same DSP that uses the same memory setup here

https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcQ272wPem32-LuGsEk-7yJt0wdYh9lrOmAl_iXHn5TgrtaHudPg

I can get clock out of pin 91 so I believe its internal oscillator is working. But apart from that no other pulse. It could be fried of stuck on HALT or RESET. I am not sure... need to investigate more.

[gkmaia]

The DSP is held in RESET by ST PI12.

When I bypassed the RESET so I would not go LOW the DSP booted up and there was activity on the memory busses and on the op amps.

The ST PI12 seems dead. The only activity I get out of it is it's oscillator running the crystal at 8MHZ.

But that is all. Did a bit of research on ST micro-controllers but could not find anything that could match what would supposedly be the VCC & VSS.

[fzabkar]

Is your mystery chip the ST92163 in your other thread?

https://www.eevblog.com/forum/repair/st92163-ic-reset-stuck-on-low/msg2636550/#msg2636550

http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXuuwxv.pdf (datasheet)

[gkmaia]

Yes it is. Have you been working on this board as well?

[fzabkar]

Yes it is. Have you been working on this board as well?

No, I've just taken an interest in your thread.

[magic]

Check supply rails and electrolytics.

If it's some oldschool MCU, one capacitor may implement an RC delay circuit resetting it on power up. Those things sometimes go bad.

[gkmaia]

I ended up implementing it like that. The cap is 20uf and it takes around a 1 sec to charge up and bring the RESET threshold to HIGH. Probably a 10uf would reduce the time but I do not have one here.

Anyway it works fine. Only bad side is if the rail goes up there is nothing to turn the IC off anymore.

But was a nice little trick anyway!